accommodate spaces in source filename (PR #84)
accommodate spaces in source filename (PR #84)

change several '%1' calls to '%~1' to remove quotes, if any, from around the source filename from the command line;
also, in constructing command-line to run FOP, put quotes around the OUTPUT_FILE name, in case the source-filename contained spaces
getreu/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,getreu/asciidoctor-fopub,getreu/asciidoctor-fopub,asciidoctor/asciidoctor-fopub